Cress is a blanket name for a number of related peppery greens in the mustard family. These greens are used in herb mixes, salads, and compound butter, among other things. Many species are very easy to grow, and they make great decorative garden plants in addition to a source of food. Greengrocers and some markets may also carry cress, although it can be extremely perishable, so it should be purchased only when it is needed.
Several different plants are considered cress, including watercress and penny cress. One species, Lepidium sativum, is more heavily cultivated than others. This species is also called garden cress, pepper cress, pepperwort, or garden pepper cress. As the names imply, this plant has a biting, sharp flavor which is quite distinctive and rather piquant. Some people also use the name for Nasturtiums.
As a general rule, all of the parts of a plant are edible. Most people use the leaves, since they are packed with iron, calcium, folic acid, and vitamins C and A. The stems, flowers, and seeds of the plants are also edible, however. In some cases, cooks use entire immature seedlings for a unique flavor, look, and texture. Typically, it is used in relatively small amounts, because the peppery flavor can get overwhelming. Especially in the Old World, cress is a very common inclusion in salads and sandwiches, since the unique and zesty flavor makes a dish more lively.
When selecting cress, look for firm, evenly colored, rich green specimens. Avoid plants with any signs of slime, wilting, or discoloration. It can be stored under refrigeration in plastic for up to five days. To prolong the life a bit, stick the stems in a water filled glass and bag the glass, refrigerating it until it is needed. Leave the greens on the stems until they are ready to be used and wash them before use to remove residual dirt and other materials.
Growing cress is remarkably easy. Soak cotton wool or peat moss in water and stuff it into a small pot. Sprinkle seeds on top, and keep them well watered until they start to sprout. Keep the plant in a light area, but not in direct sunlight, and keep watering. As it matures, you can harvest the whole young leaves or let the plant grow to a larger size so that it will develop big, peppery leaves. The cress will be usable within about five days of planting.